Geosciences Places Donated ‘Pillow Lava’ on Outdoor Display

Pillow lava at Morrill Courtyard
Pillow lava at Morrill Courtyard

After a journey of 20 miles and 450 million years, a 3-ton specimen of pillow lava has found a home on a grassy area just above the Morrill Courtyard steps.

The rock, part of what geologists call the Hawley Formation, was donated by the owners of Ashfield Stone in Shelburne Falls, Jerry Pratt and Johanna Andersen-Pratt, a UMass Amherst alumna.

Physical Plant Construction Services and members of the geology faculty traveled to Ashfield Stone to load the pillow lava on a trailer and bring it to campus.

The Pratts discovered the rock, fittingly enough, in the town of Hawley and had kept it at their Shelburne Falls fabrication shop before donating it for display. Ashfield Stone quarries, fabricates and finishes stone for interiors and landscapes.

Mark Leckie, professor of geology, says this rock is special because it preserves 450-million-year-old pillow lavas formed on the seafloor during the formation of what is now part of western Massachusetts, including the Shelburne Falls area of Franklin County.

“Pillow lavas form when very hot basaltic magma (approximately 1,150 degrees Celsius) is extruded onto the seafloor,” Leckie said. “A pillow-shaped blob of magma rapidly cools in the seawater to form a rind of glass around the ‘pillow’; another molten blob then breaks through and quickly forms another pillow. The result is an amalgamation of these pillows, which we call pillow basalts.”

They are very typical of areas of seafloor spreading, where new oceanic crust is formed, or anywhere magma comes into contact with water, he said.

The rock also can be worked into spectacularly beautiful building elements, like flooring and counter tops. About 6 feet on its longest axis, the Morrill rock displays a polished face, courtesy of Ashfield Stone.

It’s a fitting addition to the recently rebuilt courtyard, which reflects the presence in Morrill of the geosciences department and includes displays of regional rocks and a corrosion-resistant steel sculpture representing geologic time.

Andersen-Pratt, who earned her BFA with a secondary art teaching certificate, said teaching remains part of her mission with Ashfield Stone’s customers. “They might come here clutching their color samples, and all of a sudden they start noticing rocks,” she said. “They leave with a geology and history lesson.”